Bump actions/checkout from 2 to 4 (#269)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: macos-12
     steps:
       - name: checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       # See issue https://github.com/actions/setup-python/issues/577.  There is
       # some kind of environment conflict between the symlinks found in the
       # GitHub Actions runner and `brew upgrade python` where `brew` detects and
@@ -78,7 +78,7 @@ jobs:
     container: ubuntu:focal
     steps:
       - name: checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: setup
         run: ./scripts/continuous_integration/github_actions/ros_foxy/setup
         shell: bash
@@ -91,7 +91,7 @@ jobs:
     container: ubuntu:focal
     steps:
       - name: checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: setup
         run: ./scripts/continuous_integration/github_actions/ubuntu_focal/setup
         shell: bash
@@ -104,7 +104,7 @@ jobs:
     container: ubuntu:focal
     steps:
       - name: checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: setup
         run: ./scripts/continuous_integration/github_actions/ubuntu_apt/setup
         shell: bash